Quantitative Assessment of Head Motion toward Functional Magnetic Resonance Imaging during Stepping

PURPOSE: Stepping motions have been often used as gait-like patterns in functional magnetic resonance imaging (fMRI) to understand gait control. However, it is still very difficult to stabilize the task-related head motion. Our main purpose is to provide characteristics of the task-related head motion during stepping to develop robust restraints toward fMRI. METHODS: Multidirectional head and knee position during stepping were acquired using a motion capture system outside MRI room in 13 healthy participants. Six phases in a stepping motion were defined by reference to the left knee angles and the mean of superior-inferior head velocity (V(mean)) in each phase was investigated. Furthermore, the correlation between the standard deviation of the knee angle (θ(sd)) and the maximum of the head velocity (V(max)) was evaluated. RESULTS: The standard deviation of each superior-inferior head position and pitch were significantly larger than the other measurements. V(mean) showed a characteristic repeating pattern associated with the knee angle. Additionally, there were significant correlations between θ(sd) and V(max). CONCLUSIONS: This is the first report to reveal the characteristics of the task-related head motion during stepping. Our findings are an essential step in the development of robust restraint toward fMRI during stepping task.